Not Applicable
Not Applicable
(1) Field of the Invention
The present invention relates to a device for mounting on a shaft which can prevent the rotation of the shaft. In particular, the present invention relates to a device which mounts on a rotatable shaft which is part of the movement mechanism for a work surface of a workstation. The device prevents rotation of the shaft when the device is in the lock position. The device also prevents rotation of the shaft when the load on the work surface is out-of-balance.
(2) Description of the Related Art
The related art has shown various devices for controlling the rotation of a shaft in either direction using the frictional force of a wrap spring. Illustrative are U.S. Pat. Nos. 5,010,983; 5,197,704 and 5,354,028 all to Kitamura.
Kitamura ""983 describes a device for locking the rotation of a shaft in both directions using a device having a single spring mounted around a fixed shaft and a movable shaft. Further, the device does not prevent unlocking or rotation of the shaft when an out-of-balance load is applied to the shaft.
Kitamura ""704 describes an angle adjusting device for adjusting an angle of indication of a display device. The device includes a rotatable axis having small diameter end portions with a large diameter center portion spaced therebetween and a pair of fixed axis rotatably supporting the small diameter portions. A pair of coil springs having the same winding direction are mounted on the center large diameter portion and the pair of fixed axis.
Kitamura ""028 describes a device for adjusting the angle of indication of a display device. The device includes a rotatable axis rotatably supported by a fixed axis with at least one (1) coil spring closely mounted over the rotatable axis and having an end fastened on the fixed axis.
Also of interest are U.S. Pat. Nos. 4,457,406; 5,219,045; 5,441,129 and 5,568,843 all to Porter et al and 5,794,470 to Stringer which show a mechanism lock having a rod axially movable through a lock housing, with one (1) or more coil springs tightly wound about the rod and axially fixed to the housing so as to normally grip the rod against axial or longitudinal movement through the housing. A release is provided for partially unwinding the coil springs to release the rod for axial movement relative to the lock housing.
U.S. Pat. No. 4,600,240 to Suman et al describes a unidirectional friction clutch for a headrest. The headrest is rigidly secured to an axle. The axle is pivotally mounted within a U-shaped fixed bracket. The spring clutch includes a coil spring which extends over the axle. One (1) end of the spring is anchored to the fixed bracket and the opposite end is anchored to the headrest. The spring is wound around the axle to prevent clockwise rotation of the headrest since clockwise rotation tends to tighten the grip of the spring around the axle. Movement of the headrest in a counterclockwise position expends the spring which loosens the grip of the spring on the axle allowing the axle and headrest to move. Thus, this device only prevents rotation of the axle in one (1) direction. Further, the device does not prevent movement of the shaft when an out-of-balance load is applied to the headrest.
Only of minimal interest is U.S. Pat. No. 5,186,285 to van der Werff describes a device for controlling the rotation of a shaft in one (1) direction in response to a continuous torque being applied to the shaft. A control member is used to wrap and unwrap the spring. The device is not intended to control rotation of a shaft in both directions.
None of the above devices prevent unlocking of the device or rotation of the shaft when an out-of-balance load is applied to the shaft.
There remains the need for a device which prevents the rotation of a shaft in either direction when in the lock position and which can not be moved into the unlock position if an out-of-balance force is applied to the shaft.
In one (1) embodiment, the device is mounted on a shaft or axle extending between the legs of a counterbalance table or workstation. When in the active or lock position, the device prevents the shaft from rotating which prevents the movement mechanisms in the legs from raising or lowering the work surface. The device also includes an anti-release mechanism which prevents release of the device by the main release lever when an out-of-balance force is applied to the work surface such that the work surface is out-of-balance. The additional force can be applied in either direction. The force can be in the form of an additional load or less load on the work surface.
In one (1) embodiment the device includes a housing plate and a U-shaped mounting bracket with the shaft extending through the legs of the mounting bracket. A pair of fixed hubs are fixably mounted on the shaft between the legs of the mounting bracket. One of the fixed hubs is mounted adjacent the inner side of each of the legs of the mounting bracket. The fixed hubs have a first portion and a second portion. Each portion preferably has a cylindrical shape. The fixed hubs are mounted on the shaft such that the first portion of the hub is adjacent the leg of the mounting bracket and the second portion extends inward along the shaft. A rotatable hub is rotatably mounted on the shaft spaced between the fixed hubs. The rotatable hub has a first end portion, a second portion and a center portion. The rotatable hub is mounted on the shaft such that the first and second end portions extend outward toward the fixed hubs. The center portion of the rotatable hub includes an extension which extends downward toward and through an opening in the center portion of the mounting bracket. A spring wire is connected at one end to the extension. The other end of the spring wire is fixably mounted. A first and second wrap spring extend between each of the fixed hubs and the rotatable hub and are mounted over the second portions of the fixed hubs and end portions of the rotatable hub. The diameters of the second portion of the fixed hubs and the end portions of the rotatable hub are preferably only slightly greater than the inner diameter of the wrap springs such that the wrap springs are force fit over the second portions of the fixed and rotatable hub. The first end of each wrap spring adjacent the fixed hubs extend through the first and second slots in the housing plate. An anti-release mechanism is mounted on the front side of the center portion of the housing plate adjacent the slots. The anti-release mechanism preferably includes a first and second release lever and a sliding release block. The levers are pivotally mounted to the housing plate between the slots. The levers have opposed first and second ends with the pivot point located between the ends. The first release lever is mounted such that the first end of the release lever extends across the first slot and a top edge of the first end of the first release lever is in contact with the first end of the first wrap spring. The second end of the first release lever is connected to a spring which is connected at the other end to the housing plate. The spring acts to bias the first release lever into the release position. The first end of the second release lever extends adjacent the first end of the first release lever. The second end of the second release lever extends across the second slot in the housing plate and the bottom edge of the second end is in contact with the first end of the second wrap spring. The second lever is connected to one end of a spring. The other end of the spring is connected to the housing plate. The spring acts to bias the second release lever into the release position.
The sliding, release block is mounted adjacent the first ends of the release levers and is connected by a cable to the main release lever. The main release lever is preferably adjacent the front of the work surface where it is easily accessible by the user. The bottom of the slidable release block is provided with a biasing means such as a spring to bias the release block into the initial unreleased position.
Initially, the sliding release block is in the lock position and the release levers are in the release position. In this position, the wrap springs are wrapped tightly around the first portion of the fixed hubs to prevent rotation of the hubs and shaft. Thus the work surface is in a fixed position. To move the work surface, the main release lever is pulled. When the lever is pulled, the release block moves upward and contacts the first ends of the levers which acts to pivot the levers into contact with the first ends of the first and second wrap springs. The levers act on the first ends of both wrap springs in opposite directions to unwind both springs, thus allowing the fixed hubs and shaft to rotate in either direction.
The device prevents a user from releasing the device and allowing movement of the work surface when an additional load or less load (out-of-balance load) is applied to the work surface and the work surface which causes the work surface to be out-of-balance. This prevents the work surface from moving too quickly in either direction due to an extra out-of-balance load. The device preferably prevents movement of the work surface in the direction of force applied by the out-of-balance load. When an out-of-balance load is applied to the work surface a torque is applied to the shaft attempting to rotate the shaft, fixed hubs, the wrap springs and rotatable hub. The spring wire connected to the extension of the rotatable hub resists and counteracts the torque attempting to rotate the shaft and the rotatable hub and increases the amount of torque needed to rotate the rotatable hub, shaft and wrap springs. However, upon application of a torque or load on the work surface, the rotatable hub begins to rotate until the rotatable hub is in contact with the edge of the opening in the center portion of the mounting bracket. As the rotatable hub rotates, the wrap springs rotate and the first ends of the wrap springs extending through the slots in the housing plate move and pivot the release levers. When the amount of torque tending to rotate the shaft reaches a set amount the force applied to the work surface exceed a certain amount, the wrap spring have rotated such a distance as to have moved the levers such that the first ends of the levers adjacent the release block are in the non-release position. Only one (1) lever is moved, depending on the direction the shaft is rotated which depends on the direction of the out-of-balance load applied to the work surface. When the main release lever is pulled, the release block slides upward, and does not contact the lever in the non-release position. Thus, the release block will not operate to unwind the wrap spring to release the shaft in one (1) direction depending on the direction of the out-of-balance force. Consequently, the work surface can not be moved in the direction of the out-of-balance force.
In one (1) embodiment, an out-of-balance indicator is also connected to the rotatable hub. The end of the out-of-balance indicator opposite the rotatable hub is located adjacent an opening in the center stretcher panel of the table. When an out-of-balance load is applied to the work surface and the rotatable hub is rotated, the end of the indicator moves up or down to show the user that the table is out-of-balance and the direction in which the extra load is being applied. This is useful when a user changes the amount of load that on the work surface. The indicator allows the user to adjust the movement mechanisms to accommodate the change in load on the work surface.
The present invention relates to a device for controlling rotation of a shaft, which comprises: a fixed hub fixably mounted on the shaft; a rotatable hub rotatably mounted on the shaft; a wrap spring releasably mounted around the fixed hub and the rotatable hub; a stop mounted adjacent the rotatable hub to limit rotation of the rotatable hub; a release lever movably mounted adjacent the wrap spring such that the release lever is in contact with the wrap spring wherein movement of the wrap spring moves the release lever from a release position to a non-release position; and a release block slidably mounted adjacent the release lever wherein when the release lever is in the release position and the release block is moved from a lock position into an unlock position, the release block contacts the release lever and moves the release lever such that the release lever moves the wrap spring so as to release the wrap spring from around the fixed hub, wherein when the release lever is in the non-release position and the release block is moved from the lock position, the release block does not contact the release lever to release the wrap spring from around the fixed hub.
Further, the present invention relates to a device for controlling rotation of a shaft, which comprises: a first fixed hub fixably mounted on the shaft; a second fixed hub fixably mounted on the shaft; a rotatable hub rotatably mounted on the shaft; a first wrap spring mounted around the first fixed hub and the first rotatable hub; a second wrap spring mounted around the second fixed hub and the second rotatable hub; a first stop mounted adjacent the first rotatable hub to limit rotation of the first rotatable hub in a first direction; a second stop mounted adjacent the second rotatable hub to limit rotation of the second rotatable hub in a second direction opposite from the first direction; a release lever movably mounted adjacent the first and second wrap springs such that the release lever is in contact with the first wrap spring and the second wrap spring, wherein movement of the first wrap spring moves the release lever from a first release position to a first non-release position and wherein movement of the second wrap spring moves the release lever from a second release position to a second non-release position; and a release block slidably mounted adjacent the release lever wherein when the release lever is in the first release position and the release block is moved from a lock position into an unlock position, the release block will contact the release lever and will move the release lever such that the release lever will move the first wrap spring so as to release the first wrap spring, and wherein when the release lever is in the second release position and the release block is moved from the lock position into the unlock position, the release block will contact the release lever and will move the release lever so that the release lever will move the second wrap spring so as to release the second wrap spring, wherein when the release lever is in the first non-release position and the release block is moved from the lock position into the unlock position, the release block will not contact the release lever to release the first wrap spring and wherein when the release lever is in the second non-release position and the release block is moved from the lock position into the unlock position, the release block will not contact the release lever to release the second wrap spring.
Still further, the present invention relates to a device for controlling movement of a work surface of a workstation, the workstation having at least one movement mechanism having a shaft which rotates during movement of the work surface of the workstation, which comprises: a housing plate mounted to the workstation adjacent the shaft having a front side and a back side and a first and second opening; a mounting bracket having first and second ends and mounted on the back side of the housing plate such that the first and second openings are spaced between the first and second ends of the mounting bracket wherein the first and second ends of the mounting bracket have first and second holes through which the shaft is rotatably mounted; a first fixed hub fixably mounted on the shaft between the ends of the mounting bracket; a second fixed hub fixably mounted on the shaft between the ends of the mounting bracket; a rotatable hub rotatably mounted on the shaft between the ends of the mounting bracket; a first wrap spring having first and second ends and mounted at the first end on the first fixed hub and fixably mounted at the second end on the rotatable hub wherein the first end of the first wrap spring extends through the first opening in the housing plate; a second wrap spring having first and second ends and mounted at the first end on the second fixed hub and fixably mounted at the second end to the rotatable hub wherein the first end of the second wrap spring extends through the second opening in the housing plate; a first stop mounted adjacent the rotatable hub to limit rotation of the rotatable hub in a first direction; a second stop mounted adjacent the rotatable hub to limit rotation of the second rotatable hub in a second direction; a first release lever having first and second ends pivotably mounted on the front side of the housing plate so that the second end of the first release lever is adjacent the first opening in the housing plate and is in contact with the first end of the first wrap spring wherein movement of the first end of the first wrap spring moves the first release lever from a release position to a non-release position; a second release lever having a first end and a second end and pivotably mounted on the front side of the housing plate so that the first end of the second release lever is adjacent the second opening in the housing plate and is in contact with the second end of the second wrap spring wherein movement of the first end of the second wrap spring moves the second release lever from a release position to a non-release position; a release block slidably mounted on the front side of the housing plate adjacent the second end of the first release lever and the second end of the second release lever wherein when the first release lever is in the release position, and the release block is moved from a lock position to an unlock position, the release block will contact the second end of the first release lever and will pivot the first release lever such that the first release lever will unwrap the first end of the first wrap spring so as to release the first wrap spring from around the first fixed hub, and wherein when the second release lever is in the release position and the release block is moved from the lock position to the unlock position, the release block will contact the second end of the second release lever and will pivot the second release lever so that the second release lever will unwrap the second end of the second wrap spring so as to release the second wrap spring from around the second fixed hub, wherein when the first release lever is in the non-release position, and the release block is moved from the lock position to the unlock position, the release block will not contact the first release lever to release the first wrap spring and wherein when the second release lever is in the non-release position and the release block is moved from the lock position to the unlock position, the release block will not contact the second release lever to release the second wrap spring.
The substance and advantages of the present invention will become increasingly apparent by reference to the following drawings and the description.